[TC] [NETUTIL] Extend temporary errors to include those from HTTP2

What's the issue?
For some HTTP related errors/timeouts we have to perform string comparisons, in some cases these contain "net/http" which means they're only handled for the HTTP1 implementation and not HTTP2 (which is used by the GCP SDK). The knock on effect of this, is that some (known) temporary error cases are not being retried when they should be.

What's the fix?
We either:

1. Make the string comparison more generic so that it matches in both cases
2. Add the HTTP2 errors we want to retry